Method of exhaust



July 15, 1941- G. A. FREEMAN 2,249,605

METHOD 0F EXHAUST Filed Oct. 8, 1940 INVENTOR uf?. Prie/wmv ATTORNEY accordance with Patented July15, 1941 METHOD F EXHAUST George A. Freeman,

to Westinghouse Electric East Orange, N. J., asslgnor .la -Manuiacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 1940, -Serial No. 360,219

Claims.

The present invention relates to the method of seasoning lamps and particularly to lamps of the high pressure mercury type. I v Lamps .of this type havev heretofore been seasoned during exhaust on an automatic exhaust machine provided with an indexing table. In order to increase production in the interests of economy of manufacture, the various positions of the indexing table to which the lamps are moved are necessarily of shortv duration. During one of the positions of the indexing machine, the high pressure mercury lamp is connected to an exhaust pump and, while so connected, it is/customary to initiate and sustain an arc discharge between the electrodes in order to heat the same to a temperature suilicient to drive ol occluded gases, which are thus withdrawn by the vacuum pump.

However, during such automatic exhaust, the.

arcing of the electrodes is necessarily brief because of rapid indexing of the machine. As a consequence, diiiiculty in seasoning lamps of the high pressure mercury vapor type has been encountered. Investigation has shown that this difn'culty is due to the presence of hydrogen in completely driven off the electrodes which is not during the brief period of arcing on the automatic exhaust machine, and as `a-result the hydrogen is eventually evolved.. which tends to quench an arc once it has been started, and higher open circuit voltage is customarily required to maintain the arc.

`II'. is accordingly an object .of the present invention to provide a method of seasoning lamps ofthe high pressure mercury vapor type wherein the occluded gas is completely removed, which thus renders -the open circuit voltage required to be maintained substantially constant. Another object of the present invention is the method of seasoning lamps Aoi the high pressure mercury Vvapor type wherein occluded hydrogen is completely removed from the\l\amp after sealing ol! by heating the electrodes to a temperature vsuflicient v to drive on the occluded hydrogen, which is diffused through the vheated envelope and withdrawn by the vacuum pump. 1 Still further objects of the present invention will become obvious tothose skilled in the art by reference to the accompanying drawing wherein:

Fig. 1 shows aY lamp of the high pressure mercury vapor type in the iirst` step of seasoning in the present invention.

the'same lamp in the second Fig. 2 illustrates accordance with `the present seasoning step in invention wherein the electrodes'larev heated by (ci. 11s- 2).

the initiation and maintenance of an arc discharge between the electrodes. l

Fig. 3 shows the lamp of Fig.1 in the` third `s 'easoning step of the present invention wherein the lamp is cooled and exhausted.

Fig. 4 shows the lamp in the fourth step` in seasoning of the lamp in accordance with the present invention. i y

Fig. 5 illustrates the lamp in the fifthV step in seasoning` of the same. in accordance with the present invention. v

Fig. 6 illustrates an apparatus for housing the lamps during seasoning in accordance with vthe present invention. y

Referring now to theA drawing inl detail, the lamp as shown in Fig. lis of the type shown and described more in detail in the copending application, Ser. No. 284,576,viiled July 15, 1939, of which 1 am a co-inventor, and which is assigned to the same assignee as .the present invention.

-Since the present invention is not directed to per se, it is ybelieved be herein described the structureof the lamp unnecessary that the same indetail. .Y v

It should suffice to say that the lamp comprises an envelope 5A composed of Aa `vitreous material, such asI quartz or a material `having 80% or more of quartz, which is capable` of withstanding the high temperatures during operation of the lamp. The envelope 5 as shown is provided with a pair of electrodes 6 and 'I sealed :therein and supported B which are suspended between a pair of leading-in and supporting conductors I0 and I2. e

These leading-in and supporting conductors are sealed. into a press portion I3 forming part of an outer surrounding envelope I4, with the latter being'provided with an exhauststem I5 for exhaust purposes. The electrode 6 as shownis connected to the leading-in conductor -III by a flexible conductor. I6, and .theelectrode 1 is connected by a 'similarv flexible conductor I ,1- to the leading-in conductorl I 2.

45 is connected through an impedancedevice I9 to A starting electrode I8 the leading-in conductor III., I

= Each endv of the; quartz envelope 5 is provided with a metallic reiiecting shield20 for thepurpose of conserving heat..v The high pressure .mer-

f. cury vapor lamp 5, as is customary in the art,

is first exhaustedon an automatic exhaust machine provided with anindexing table, as above noted: In one o f the positions of. theindexing table and while the quartz envelope 5 .is con- 1 nectedr to a vacuum pumppa potential is applied to the electrodes to initiate and sustainan arc heating of the electrodes by the discharge, the

hydrogen is eventually driven off, which tends to quench the arc, thus requiring higher open circuit voltage to maintain the arc. overcome this difficulty, the method of the pres- In order to` ent invention comprises arcing the lamps during exhaust of the outer surrounding envelope. In carrying out such method, the sealed lamp 5 is accordingly mounted in the outer envelopev and the latter. connected to a vacuum pump, in the manner shown schematically .in Fig. 1. After vthe outer envelope is subjected to a vacuum pump for a short period of time, a high voltage current is applied to the electrodes 6 and 1 of the lamp 5 from a suitable source of supply, such for example as a high voltage transformer 23, the primary windingl24 ofwhich maybe connected to a source of'supply vof the customary'domestic potential of 115 or 230 volts.

'The secondary winding 25 which generates approximately 500 volts is connectedl to the leadingin conductors l0 and I2 and thus to the electrodes 6 and 'l of the lamp 5. An impedance device 26 is provided in series with the lamp 5 and the secondary winding to limit the arcing current and, as shown schematically in the several figures, one or more lamps may be simultaneousj lyseasoned by connecting the lamps in a series circuit.

Upon vclosure' of a suitable switch 21, the high voltage current will accordingly be applied to the electrodes 6 and 1^, whichinitiates a discharge therebetween. 'I'his discharge is continued for' a period of approximately five minutes.' with the result that the electrodes 6 and 'I are heated to a temperature suiiicient to drive ofi" occluded gas, and particularly hydrogen.

Since the quartz envelope 5 isalso heated by the discharge to va relatively high temperature, the hydrogen diffuses through the -heated wall of the quartz envelope into the outer envelope Il and, sincethe latteris in direct communication with the vacuum pump during the continuance of the discharge, the gas diffused through the quartz envelope is thus withdrawn from the outer envelope Il.

At the same time, the heat generated by the The outer envelope I4 may then be filled with an inert gas such as nitrogen, if desired, after be adequately baked by the heat generated by the discharge, the several lamps may be housed within a container 28, such as Vshown in Fig. -6. It will thus be seen that by employing the method herein described, the high pressure mercury vapor lamp may be partially seasoned on an automatic exhaust machine and completely sealed off, after which it can be completely seasoned during exhaust of the outer envelope, thus removing all of the gas which might otherwise diffuse back into the discharge lamp during life.

It can thus be' readily seen that a lamp is produced by the present method wherein the oper circuit voltage required to maintain the arc remains substantially constant during the entire life of the lamp. Moreover, arcing of the lamp while on the automatic exhaust machine may be eliminated if desired and seasoning of the eleotrodes carried out entirely during exhaust of the outer envelope.

. In addition, by seasoning the high pressure Vmercury vapor lamp during exhaust of the outer envelope, the latter is heated to a temperature sufficient to bake the moisture therefrom without the necessity for an oven bake as heretofore required, which thus materially decreases the entire manufacturing cost of seasoning and exhausting. f.

Although one specific embodiment of the present inventionhas been shown and described, it is to be` understood that still further modifications of the same may be made without departing from the spirit and scope of the appended claims.

I claim:

1. The method of` seasoning high pressure mercury vapor lamps which comprises sealing oif the quartz envelope containing the electrodes, mountingI thesealed envelope in an outer envelope, energizing the lamp to initiate and sustain an arc discharge between the electrodes to heat the latter to a temperature sufficient to drive off occludedgas and cause the latter to diffuse through the heated quartzv envelope, exhausting the outer envelope during the continuance ofthe discharge for a period of time suf.

iicient to remove .the gas therefrom, and sealing ofi' the outer envelope.

- 2. The method of seasoning highpressure merclu'y vapor lamps which comprises sealing oir the quartz envelope containing the electrodes, mounting the sealed envelope in an 'outer envelope,

energizingvthe lamp to initiate and sustain an arc discharge between the electrodes to heat the latter to a temperature sumcient to drive of! occluded gas and cause the latter to diifuse through therefrom, introducing inert" gas into the outer envelope, and sealing off the outer envelope.

which thelamp is tipped off, as shown in F18. 5.

As Vpreviously mentioned, two or more lamps may simultaneously b e seasoned and in order to conserve heat .s o'that the outer envelope Il will 3. The method of seasoning high pressure mercury v apor lamps which comprises applying electrical energy to the electrodes sealed into a quartz envelope to initiate and sustain an arc discharge therebetween for a short period of time to heat the electrodes and drive oif occluded gas, ex-

hausting the quartz envelopeduring continuance V of the short period of the discharge, sealing-off the quartz envelope, mountingh the lamp in an outer envelope; again applying electrical energy to the electrodes of the lamp to initiate and sustain an arc dischargetherebetween for a substan tially longer period of time to heat the electrodes to a temperature sumciently high to drive oir substantially all remaining occluded gas and cause the latter to diffuse through the heated quartz envelope. exhausting the outer envelope during the continuance of the discharge, and sealing-off the outer envelope.

4. 'I'he method of seasoning high pressure mercury vapor lamps which comprises sealing-olf the quartz envelope containing the electrodes, mounting the sealed envelope in an outer envelope, applying a high voltage current to the electrodes of the lamp to initiate and sustain an arc discharge therebetween to simultaneously heat the electrodes to a temperature suicient to drive oi occluded gas/'and cause the latter to diffuse through the heated quartz envelope and to bake the outer envelope bythe heat from the discharge, exhausting the outer envelope during the continuance of the discharge for a period of time suicient to remove the gas therefrom, and sealing-oli the outer envelope.

5. The method of seasoning high pressure mercury vapor lamps which comprises applying electrical energy to the electrodes sealed into a quartz envelope to initiate and sustain an arc discharge therebetween for a short period of time to heat the electrodes and drive oi occluded gas, exhausting the quartz envelope during continuance of the short period of the discharge, sealing-0E the quartz envelope, mounting the lamp in an outer yby the heat from the discharge, exhausting the outer envelope during the continuance of the discharge for a period of time sucient to remove the gas therefrom, introducingan inert gas into the outer envelope, and sealing-oft the outer envelope.

GEORGE A. FREEMAN. 

